1. Field of the Invention
The present invention relates to a novel organopolysiloxane, a process for producing the same and a curable resin composition containing the organopolysiloxane as an effective component. A curable resin composition containing the novel organopolysiloxane as an effective component has distinguished transparency, luster, peelability, surface lubricity and water and oil repellency, and therefore is useful as a resin for mold-releasable paper, a coating agent, an anticorrosive agent for printed substrates, etc.
2. Related Art Statement
Organopolysiloxanes having acryloyl groups or methacryloyl group (both groups together being hereinafter referred to as (meth) acryloyl groups) at the terminals thereof and/or as side chains are distinguished in polymerization reaction and UV curing, and thus are used as a resin for mold-releasable paper, a coating agent, an anticorrosive agent for printed substrates, etc.
It has been known that these organopolysiloxanes can be produced by reaction of, for example, a tri(meth)acrylate compound having --COH groups with an organopolysiloxane having SiZ groups, where Z is an alkoxy group, a hydroxy group or a chlorine atom (U.S. Pat. No. 4,301,268).
However, the organopolysiloxanes so produced have SiOC-- bonds and thus are liable to be hydrolyzed.
A process for producing an organopolysiloxane by reaction of (meth) acrylic acid with an organopolysiloxane having epoxy groups in the molecule has been also known (JP-A-2-45533). However, the process has a difficulty in reaction control due to a very large heat of reaction.
It has been also known to produce organopolysiloxanes by hydrosilylation reaction of an organopolysiloxane having SiH groups with (meth)acryloyl groups of a compound having a plurality of (meth)acryloyl groups (the compound being hereinafter referred to as (meth)acrylate compound) in the presence of a platinum catalyst [Journal of Applied Polymer Science, 47, 1309-1314 (1993)]. However, the hydrosilylation reaction is applied to a dimethylsiloxane-methylhydrogen siloxane copolymer as shown by the following formula (IV) (which will be hereinafter referred to as PDMHMS), that is, an organopolysiloxane having SiH groups as side chains: ##STR1## Thus, the hydrosilylation reaction produces only organopolysiloxanes having (meth)acryloyl groups as side chains and further has the following problem.
That is, the starting material PDMHMS is a copolymer and the number and positions of the SiH groups in one molecule are largely fluctuated, and thus it is hard to control the hydrosilylation reaction and also to control the properties of the resulting organopolysiloxanes. Furthermore, the PDMHMS used in the hydrosilylation reaction is less compatible with the (meth)acrylate compound, and thus a relatively large amount of the catalyst is required for satisfactory hydrosilylation reaction. Particularly when a trimethylolpropane triacrylate (which will be hereinafter referred to as TMPTA) useful for endowing the resulting organopolysiloxanes with various properties is used as the (meth)acrylate compound, it is necessary to use an organic solvent besides the large amount of the catalyst. In that case, the resulting organopolysiloxanes often become white turbid and thus are very inconvenient for use, for example, as a coating material.